<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>二级菜单</title>
    <style>
        * {  
    margin: 0; 
    padding: 0; 
    border: none; 
    text-decoration: none;
    list-style: none;
}
        a { text-decoration: none; }
       .nav {
        background-color: gray;
        height: 50px;
        line-height: 50px;
        text-align: center;
       }
       .list1 {
        float: left;
        width: 100px;
       }
       .list a {
        color: white;
       }
       .list .list3 li {
        background-color: gray;
        height: 40px;
        display: none;
       }
       .list1:hover li {
        display: block;
       }
    </style>
</head>
<body>
    <div class="nav">
        <ul class="list">
            <li class="list1"><a href="#">视频</a>
             <ul class="list3">
                <li><a href="#">爱奇艺</a></li>
                <li><a href="#">优酷</a></li>
                <li><a href="#">腾讯视频</a></li>
             </ul>   
            </li>
            <li class="list1"><a href="#">购物</a>
                <ul class="list3">
                    <li><a href="#">京东</a></li>
                    <li><a href="#">淘宝</a></li>
                    <li><a href="#">天猫</a></li>
                </ul>
            </li>
        </ul>
    </div>
</body>
</html>